(a) Field of the Invention
The present invention relates to an objective lens system for microscopes having a long working distance, aberrations correctly favorably to peripheral portion of visual field and a numerical aperture (NA) of 0.4.
(b) Description of the Prior Art
Generally speaking, objective lens systems for microscopes having longer working distances are more convenient for microscopy. Further, for microscopy with high resolution even at periphery of the visual field, it is necessary to design objective lens systems so as to have NA as large as possible and correct curvature of field favorably even at periphery of the visual fields.
As a conventional objective lens system for microscopes having a long working distance and an NA of 0.4, the one disclosed by Japanese unexamined published patent application No. 128154/77 has already been known to those skilled in the art. However, this objective lens system has a defect in that it cannot form a favorable image at periphery of the visual field due to remarkable curvature of field.